Voluntary action: subjective experience and brain processes

Abstract

Humans interact with the world through voluntary, goal-directed action. A phenomenal corollary of this capacity is the sense of agency. This refers to the conscious experience one has of one's own agency; the sense in which actions and their results are caused or controlled by one's ‘Self’.
Recent accounts have tended to emphasise either the role of efferent processes within the motor system or the role of general-purpose inferential mechanisms in the sense of agency. In this thesis these different accounts of agency, and their neural substrates, were systematically investigated. It was found that the sense of agency is best understood as a combination of both mechanisms. Several factors selectively influencing the two mechanisms were identified across a series of behavioural experiments in healthy volunteers. Physiological experiments confirmed the efferent contribution to the sense of agency, and identified it with the pre-supplementary motor area.
The importance of the sense of agency to normal human functioning can be seen in certain disorders. Abnormal sense of agency profoundly impacts the overall sense of self and also social functioning. This thesis investigated the sense of agency in Schizophrenia and Parkinson's disease. Abnormalities in the sense-of agency were found in both clinical groups, and these abnormalities were explained by known pathophysiology and cognitive impairments in these groups.